Given the value of Rydberg constant is 107 m-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be:

  • Option 1)

    0.025 x 104 m-1

  • Option 2)

    0.5 x 107 m-1

  • Option 3)

    0.25 x 107 m-1

  • Option 4)

    2.5 x 107 m-1

 

Answers (1)

 

Balmer series -

frac{1}{lambda }= Rleft ( frac{1}{2^{2}}- frac{1}{n^{2}} 
ight )

left ( : visible : light 
ight )

- wherein

n=3,4,5-----

When electron jump from higher orbital to n=2 energy level

 

 

Balmer series n\rightarrow 2

last line of Balmer series means when e^{-}   jump from infinity \rightarrow 2

\therefore \frac{1}{\lambda }= R\left ( \frac{1}{4}-\frac{1}{\infty } \right )=\frac{R}{4}

Wave number =\frac{1}{\lambda } = \frac{R}{4}

=0.25\times10^{7}\:m^{-1} 

 


Option 1)

0.025 x 104 m-1

This option is incorrect.

Option 2)

0.5 x 107 m-1

This option is incorrect.

Option 3)

0.25 x 107 m-1

This option is correct.

Option 4)

2.5 x 107 m-1

This option is incorrect.

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